Possible origins of the low-temperature anomaly in CeRu₂

The magnetic-field dependence of DC susceptibility and specific heat of polycrystalline CeRu₂ has been studied. The superconducting transition temperature (T_c) of the sample is 6.2 K. An extraordinary anomaly was observed at the T ∼ 6 K in the absence of magnetic field (H), and T is suppressed slightly with increasing H. Such an anomaly can be most probably attributed to the existence of few amounts of CeRu₂ nano-clusters embedded in the bulk or the magnetic ordering of impurity phase Ce_xRu_y. The T is actually a superconducting transition, which has a higher critical field than the bulk CeRu₂.